Pressure regulating and reducing gas-flow meter for industrial installations

ABSTRACT

Pressure regulating and reducing gas-flow meter device allowing to supply gas at a variable rate of flow and under a predetermined pressure from a source of gas under a higher pressure. The device comprises arranged in series : a pressure reducing and regulating device provided with a pilot circuit, a sonic nozzle mounted downstream of the said regulating device and supplied thereby, and means for measuring the conditions of flow, in the interval comprised between said regulating device and said nozzle, which conditions enable the rate of flow through the apparatus to be measured.

United States Patent Castillon 51 May 30, 1972 [54] PRESSURE REGULATINGAND REDUCING GAS-FLOW METER FOR [73] Assignee: Gaz De France, Paris,France [22] Filed: Mar. 12, 1971 [21] Appl. No.: 123,588

Primary Braminer-Henry T. Klinksiek Attorney-Kenyon & Kenyon Reilly Carr& Chapin [57] ABSTRACT Pressure regulating and reducing gas-flow meterdevice allowing to supply gas at a variable rate of flow and under apredetennined pressure from a source of gas under a higher pressure. Thedevice comprises arranged in series a pressure reducing and regulatingdevice provided with a pilot circuit, a sonic nozzle mounted downstreamof the said regulating device and supplied thereby, and means formeasuring the 73/199 conditions of flow, in the interval comprisedbetween said regulating device and said nozzle, which conditions enablethe [58] Field of Search 1 37/55 I 501, 505.22, 73/199 rate offlowthrough the apparatus to be measured. [56] References Cited UNITEDSTATES PATENTS 6 Claims, 6 Drawing Figures 3,021,684 2/1962 Berck..73/l99 X 1s P O 0) 41 (O Patented May 30, 1972 2 Sheets-Sheet 1 (PO7T0) my VHNTOR PH/L IHOE CHARLES '41 550704: m 4 01V Patented May 30,1972 z shun-sum 2 PH. #2 5 61/404 55 rik 5527 CH5 77L LON PRESSUREREGULATING AND REDUCING GAS-FLOW METER FOR INDUSTRIAL INSTALLATIONS Thepresent invention has essentially for its object a pressure regulatingand reducing gas-flow meter device allowing to supply gas at a variablerate of flow and under a predetermined pressure adjustable for instanceto a substantially constant value, to any industrial installation from asource of gas under a higher pressure, and to simultaneously measurewith a high accuracy the amount of gaseous fluid supplied to the saidinstallation. The device according to the invention may beadvantageously used for the measurement of very high rates of flow, forinstance the rate of flow of a combustible gas supplied at each momentat the start of a network.

In the usual practice, a network constituting a circuit for the supplyof user apparatuses is supplied from a source of gas at a higherpressure, owing to an installation comprising a pressure regulating andreducing device which comprises a pilot circuit, the informationtake-off means of which are located in the circuit supplying the saidapparatuses and allows at every moment to keep the pressure in thedistribution network substantially constant at a set point or value,irrespective of the flow called for (withina certain range). In such aninstallation it is extremely difficult, with the known devices, toaccurately measure the rates of gas flow supplied to the network. Inparticular, theknown apparatuses used to measure such rates of flow arevery sensible to pressure variations and to various disturbances inducedin the distribution network. Moreover, such apparatuses are extremelycomplicated, delicate and expensive.

The pressure distributing and reducing meter device according to theinvention does not give rise to such difficulties.

The said meter device is characterized in that it comprises thefollowing members arranged in series a pressure reducing and regulatingdevice provided with a pilot circuit, at least one sonic nozzle mounteddownstream of the said pressure reducing regulating device and suppliedthereby,- a probe placed downstream of the said nozzle and transmittingto the said pilot circuit the necessary information for the regulationof the said pressure-reducing and regulating device, and means formeasuring the conditions of flow, such as the temperature and pressurein the interval comprised between the said reducing and regulatingdevice and the said noule, which conditions enable the rate of flowthrough the apparatus-to be measured.

It is indeed known that the rate of discharge of a sonic nozzle dependssolely upon the conditions of pressure P, and temperature T existingupstream of the noule, and upon the specific gravity d of the gasrelative to dry air at C. and at a pressureof 760 millimeters ofmercury, or upon the density p measured under the conditions existingupstream of the nozzle, according to the following theoreticalrelationships I wherein Q; is the volumetric rate of flow,

Qm C2 JITAPA wherein Q, is the mass rate of flow, C and C being constantcoefficients called discharge coefficients when the gas is a perfect orideal one. With a real gas, the said coefficients slightly varyaccording to the upstream conditions, known value tables being availablefor use.

Where a pressure regulating and reducing gas-flow meter device accordingto the invention is used, the following advantages are immediatelyobtained the device readily adapts itself to any demand variations,owing to the fact that the reducing device'pilot probe placed downstreamof the nozzle so controls the progressive opening or closing of thereducing device that the pressure downstream of the nozzle, i.e. the onedelivered to the circuit supplying the apparatuses, always remainsconstant the metering accuracy is excellent, for it is sufficient, inorder to determine the rate of gas flow, to measure the mag nitudes P Tand d if it is desired to determine the volumetric rate of flow, and themagnitude P and p if it is desired to determine the mass rate of flow.In particular, it is no longer necessary, as in the known measuringdevices using flow meters under subsonic conditions, to measure the lossof pressure in the nozzle at every moment, a measurement which is knownto be very difficult to perform. The measurement is all the moreaccurate as the sonic throat of the nozzle renders the circuit upstreamof the nozzle independent of the downstream circuit, so that themeasurement is not liable to be disturbed by pulses possibly induced inthe distribution network. Means for damping or preventing disturbingfeed-back phenomena at certain resonance frequencies may possibly beprovided in the control circuit of the reducing device. The damping ofsuch phenomena may also be obtained,for instance, by selecting for thereducing device a membrane or diaphragm offering suflicient inertia thecost of the device is considerably reduced owing to the fact that themeter is reduced, according to the invention, to at least one sonicnozzle and to simple pressure and temperature measuring apparatusesarranged between the reducing device and the nozzle. An integratingdevice directly converts the measured pressure and temperature valuesinto rate-of-flow values;

the device operates as a flow limitingdevice preventing a flow higherthan a predetermined limit value from being called into the upstreamnetwork, the said limit value being adjustable according to thearrangement of the installation as will be explained later thereproductibility of the indications of the device is very high, owing tothe fact that it comprises no delicate member, thus renderingmaintenance operations simpler and less expensive.

Advantageously and according to another feature of the invention,several sonic nozzles are mounted in parallel and provided in theircircuits with a cut-off member such as a valve or the like. Such aparallel connection of several nozzles enables the flexibility in use ofthe measuring device as well as the range of measurable rates of flow tobe increased.

The invention will be better understood and other objects,characteristics and advantages thereof will appear as the followingdescription proceeds, with reference to the appended drawings givensolely by way of example illustrating several forms of embodiment of theinvention and wherein FIG. 1 is a diagrammatic view of a pressureregulating and reducing gas-flow meter device designed according to theinvention;

FIG. 2 shows diagrams illustrating the operation of the device of FIG. 1

FIG. 3 is a view similar to that of FIG. 1 relating to a modified formof embodiment'of a device according to the invention, comprising twosonic nozzles connected in parallel FIG. 4 shows curves illustrating theoperation of the device of FIG. 3

FIGS. 5 and 6 are views similar to those of FIGS. 1 and 3, relating totwo other modified forms of embodiment of a device according to theinvention.

According to the form of embodiment illustrated in FIGS. 1 and 2, apressure regulating and reducing flow-meter device according to theinvention enables gas to be supplied to a circuit or network 11 fordistributing the same to user apparatuses (not shown) from a circuit 10connected to a source of gas at a higher pressure (not shown), the saiddevice being at the same time adapted to regulate the pressure of thesaid gas and to meter the rate of flow supplied. Usually, in such distribution networks, the pressure P and the temperature T of the supplygas are substantially constant, and it is desired to maintain thedistribution pressure P,, at the inlet of the network 1 l at asubstantially constant value.

In order to reduce the pressure of the gas from the value P to a lowerset value P, which may be varied according to needs, use is made of aregulating and reducing device 12. In a manner known per se, the lattercomprises a pilot circuit 13 which controls the same and the informationtake-off means 14 of which is placed in the supply circuit 11 of theapparatuses. Thus, if as a result of an increase in demand, the pressurel, tends to diminish in the network 11, the reducing device 12controlled by its control circuit 13 opens in order to supply a greatergas flow and restore the pressure P, to the said set value. Inversely,if the demand diminishes and the pressure I, tends to increase, thereducing device 12 controlled by its circuit 13 tends to close.

In the complex metering distributing and reducing device according tothe invention, a sonic nozzle 16 is mounted in the circuit 15 connectingthe reducing device 12 to the circuit 1 1.

In the circuit 15 between the reducing device 12 and the nozzle 16 aremounted measuring means diagrammatized at 40, 41 for measuring forinstance, respectively, the pressure P, and the temperature T in thecircuit 15 downstream of the reducing device 12 and upstream of thenozzle 16.

Owing to the sonic character of operation of the nozzle 16, the rate offlow passing therethrough is determined at each moment by the previouslymentioned formulas Qv l( A/ 421-) as far as the volumetric rate of flowis concerned,

Qm C2 JP: PA as far as mass rate of flow is concerned.

Knowing the nature of the gas distributed and, therefore, its specificgravity d (relative to dry air at C. and at 760 millimeters mercurypressure) and also its density p, (under the temperature and pressureconditions prevailing in the circuits the volumetric or the mass rate ofgas flow passing through the circuit 15 at every moment may thus bedetermined immediately in an integrating device 42 according to themeasured pressure value P and temperature value T The integrating device42 effects the rate-of-flow measurement irrespective, in particular, ofthe loss of pressure resulting from the presence of the nozzle 16 in thedistribution network.

The two curves illustrated in FIG. 2 show respectively, the volumetricrate of gas flow Q as a function of the pressure P respectively for thereducing device 12 and the nozzle 16. The curve 17 is first composed ofa substantially horizontal flat portion until the pressure substantiallyreaches the value P /2. At the end of this flat portion, the rate offlow Q diminishes until it is reduced to zero when the pressure P,reaches the value P upstream of the reducing device.

The curve 18 is a straight line extending in prolongation of a parabolaarc passing through the point of origin (not shown) and corresponding tothe subsonic conditions of flow. As a matter of fact, the noule operatesunder sonic conditions only above a certain minimum rate of flow Q,corresponding to a pressure P,. It is desirable to reduce Q, and,therefore, P, to a minimum, and this is readily obtained by using anozzle having a sufficiently long diffuser cone of 7. In this case, P,may come down to a value equal to 1.05 P The point W of intersection ofthe curves 17 and 18 shows the maximum rate of flow 0, which may passthrough-the reducing device and the nozzle mounted in series, the rateof flow Q corresponding to a maximum pressure P, equal to P Theinstallation therefore operates correctly at all rates of flow Q,comprised between Q, and Q The rate of flow Q, is determined by thevalue P of the pressure P existing in the circuit 15. The nozzle 16 actsas a means limiting and determining the flow passing through the device.In addition, it ensures a certain reduction of the gas flow whichcomplements the reducing action of the reducer 12. In addition undersonic working conditions, the pressure P,, and temperature T conditionsupstream thereof vary as a function of the rate of flow passingtherethrough, and this rate of flow can be calculated directly and in asimple manner by simply measuring the said conditions.

According to the modified form of embodiment illustrated in FIGS. 3 and4, wherein the similar parts of both installations are indicated in thesame manner, the single nozzle 16 of FIG. 1 is replaced by two nozzles20, 21 mounted in parallel in the circuit 15 proceeding from thereducing device 12. The nozzles 20, 21 open into the distributioncircuit or network 11 through the medium of closing members such as thevalves 22, 122 controlling the nozzle and 21, respectively.

FIG. 4, in the same manner as FIG. 2, shows the curve 17 characterizingthe operation of the reducing device 12, a curve 23 characterizing theoperation of the nozzle 20, a curve 24 characterizing the operation ofthe nozzle 21 and the curve 25 corresponding to the sum of the flows ofcurves 23 and 24.

At low rates of flow, the valve 122 is closed and only the sonic nozzle20 is operated. The rates of flow may then be stepped between a minimumvalue Q, corresponding to the minimum threshold of operation of thenozzle 20 and a maximum value 0;, corresponding to the point X ofintersection of the curves 17 and 24 as explained in connection withFIG. 2. At values higher than Q and lower than 0, corresponding to theordinate of the point Y of intersection of the curves 17 and 24, thevalve 22 is closed and the valve 122 is opened, so that the gas flowpasses only through the nozzle 21. It should be noted in FIG. 4 that thecurve 24 characterizing the nozzle 21 is so selected that the minimumrate of flow Q, corresponding to its threshold of operation isconsiderably lower than the rate of flow Q so that the nozzle 21operates under sonic conditions immediately after switching. Inaddition, in order to avoid having to pass too frequently from onenozzle to the other in the range of flow rates close to Q it isnecessary that the nozzle 21 may operate under sonic conditions at flowrates considerably lower than Q The extent of the switching range may beadjusted by means of the valves 22, 122. Unstable operation phenomenasuch as pumping phenomena in the installation are thus avoided.

At flow rates higher than Q4, both valves 22, 122 are opened, themaximum flow O: which can pass through the installation corresponding tothe ordinate of the point Z of intersection of the curves l7 and 25. Allthe operations of opening and closing of the valves 22 and 122 areadvantageously controlled automatically, according to the flowsadmitted, by the variations of the pressure P,,.

The measurement of the rate of flow passing through the installation isperformed, as in FIG. 1, starting from the apparatuses 40, 41 formeasuring the values P, and T and the integration of these values in theintegrating device 42.

In the modified form of embodiment illustrated in FIG. 5, it is seenthat to an installation whose structure is identical with that of FIG.1, is adjoined an additional sonic nozzle 26 connecting the supplysource circuit 10 to the distribution network circuit 11. Otherwisestated, the additional sonic nozzle 26 is mounted in parallel on theregulating and reducing meter (comprising the regulating and reducingdevice 12, the nozzle 16', the control means 13 and the measuringdevices 40, 41, 42) connecting the source of gas at a pressure Pdirectly to the supply circuit at a pressure P A valve 27 placed in thecircuit 28 of the nozzle 26 enables the latter to be cut-off.

Since the nozzle 26 is a sonic nozzle and the supply conditions(pressure P and temperature T of the supply source are constant, aconstant gas flow is admitted through the circuit 28 (the said constantflow depending only upon the conditions upstream of the nozzle, i.e. thepressure P and the temperature T of the gas).

By selecting for this flow a value substantially equal to the maximumflow Q which may pass through the nozzle 16, the distributing andmetering capacity of the installation may, as a first approximation, bedoubled.

Indeed, at rates comprised between Q, and Q2 (FIG. 2) the valve 27 isclosed, the circuit 11 being supplied only by the nozzle 16.

At values higher than 0,, the valve 27 is open and a constant flow Q isadmitted in parallel with the flow of the nozzle 16'.

The measurement of the flow rate according to the measured values of thevariables P and T and the regulation of the flow as it passes throughthe nozzle 16 and the reducing device 12 are performed as describedpreviously. To the variable flow determined by the integrating device 42is added the constant fiow Q passing through the nozzle 26.

According to the modified form of embodiment illustrated in FIG. 6, thesonic nozzle 26 of FIG. 5 is replaced by a set of sonic nozzles 29 to32, each of which may be cut ofi or put into operation by a controlvalve 33 to 36.

The nozzles 29 to 32 are each used individually like the nozzle 26.Advantageously, their flow rates are stepped and the control of thevalves 33 to 36 is performed automatically and may be made to dependupon a minimum value and maximum value of pressure P In practice, inorder, on'the one hand, to avoid unsteady operation phenomena and, onthe other hand, to operate the nozzles 16' (FIG. 5) or 16" (FIG. 6)alternately at low and high flowrates (close to Q and Q respectively asshown in FIG. 2), the nozzles 16', 16" in an installation of the typeillustrated in FIGS. 5 and 6 are advantageously replaced by a pair ofassociated nozzles as shown in FIG. 3. The sequence of operation ofthese various nozzles is then suitably selected. The flow rates of thenozzles 26 (FIG. 5) and 29 to 32 (FIG. 6) should also be so selectedthat every time one of them is switched the sonic nozzles mounted in thecircuit operate within a range comprised between their minimum flow rateand their maximum flow rate.

It should be noted that owing to the interposition in the distributionnetwork, upstream of the user apparatuses, of one or several nozzles inparallel arrangement, all the devices described above offer theadvantage of ensuring an automatic limitation of the flow, which cannever exceed the sum of the maximum flows passing through the variousnozzles under the supply conditions P T of the installation. The flowcalled for in the downstream network may thus be limited at any momentirrespective of the conditions existing in the latter.

What is claimed is 1. Pressure regulating and reducing meter device forthe supply of a gas fluid at a variable rate of flow and a substantiallyconstant pressure, in particular for an industrial installation, from asource of gas at a higher pressure, comprising arranged in series apressure regulating and reducing device provided with a pilot circuit,at least one sonic nozzle mounted downstream of the said regulating andreducing device and supplied by the latter, a probe placed downstream ofthe said nozzles and transmitting to the said pilot circuit theinformation for the regulation of the said regulating and reducingdevice, and means for measuring the conditions of flow, such as thetemperature and pressure in the interval comprised between the saidregulating and reducing device and the said nozzle, the said conditionsbeing supplied to measuring means for enabling the flow passing throughthe apparatus to be measured.

2. Device according to claim I, wherein the said probe supplies to thepilot circuit the measured value of the pressure existing downstream ofthe nozzle and the said regulating and reducing device is so controlledby the said measured value as to keep the said pressure equal to the setvalue at the point of measurement.

3. Device according to claim 1, comprising several said sonic nozzlesmounted in parallel and provided in their circuit with a cut-off valvemember.

4. Device according to claim 3, wherein the dimensions of the nozzlesare stepped.-

5. Metering, distributing and pressure-reducing device for the supply ofa gas fluid at a variable rate of flow and a predetermined pressure froma source of gas at a higher pressure comprising in addition to apressure regulating and reducing meter device as described in claim 1,at least one additional sonic nozzle mounted in parallel with the saidpressure regulating and reducing meter device, the said auxiliary nozzleconnecting the source of gas under pressure directly to the supplycircuit of the industrial installation, a cut-off valve member beingmounted in series with the said auxiliary nozzle.

6. Device according to claim 5, comprising several said additionalnozzles, the dimensions of which are stepped, mounted in parallel, eachsaid additional nozzle being provided with an associated cut-off device.

1. Pressure regulating and reducing meter device for the supply of a gas fluid at a variable rate of flow and a substantially constant pressure, in particular for an industrial installation, from a source of gas at a higher pressure, comprising arranged in series : a pressure regulating and reducing device provided with a pilot circuit, at least one sonic nozzle mounted downstream of the said regulating and reducing device and supplied by the latter, a probe placed downstream of the said nozzles and transmitting to the said pilot circuit the information for the regulation of the said regulating and reducing device, and means for measuring the conditions of flow, such as the temperature and pressure in the interval comprised between the said regulating and reducing device and the said nozzle, the said conditions being supplied to measuring means for enabling the flow passing through the apparatus to be measured.
 2. Device according to claim 1, wherein the said probe supplies to the pilot circuit the measured value of the pressure existing downstream of the nozzle and the said regulating and reducing device is so controlled by the said measured value as to keep the said pressure equal to the set value at the point of measurement.
 3. Device according to claim 1, comprising several said sonic nozzles mounted in parallel and provided in their circuit with a cut-off valve member.
 4. Device according to claim 3, wherein the dimensions of the nozzles are stepped.
 5. Metering, distributing and pressure-reducing device for the supply of a gas fluid at a variable rate of flow and a predetermined pressure from a source of gas at a higher pressure comprising in addition to a pressure regulating and reducing meter device as described in claim 1, at least one additional sonic nozzle mounted in parallel with the said pressure regulating and reducing meter device, the said auxiliary nozzle connecting the source of gas under pressure directly to the supply circuit of the industrial installation, a cut-off valve member being mounted in series with the said auxiliary nozzle.
 6. Device according to claim 5, comprising several said additional nozzles, the dimensions of which are stepped, mounted in parallel, each said additional nozzle being provided with an associated cut-off device. 